4.6 Tape and Disk Management

Tape and Disk Management is controlled by the parameters setup in the profile definition files (see section 3.7 on page 3-8).  Whether backups go to disk or tape is setup when you define the backup.  However, the source of tapes, the retention of backups and the cycling of resources is defined in these files on the Storage Reservoir.

If you are running backups to disk, each backup (full or incremental) is placed on one disk file per backup in the <workpath>\backups\<backup profile> directory with the file name <versiondate>’f’ (full) or ‘i’ (incremental)>.backup.  You can adjust this destination by specifying a DISKBACKUPPATH in your profile definition file; then backups will be written to this path with the backup profile as the first dotted component of the file name.  If there is insufficient space in the DISKBACKUPPATH (based on the size calculation from the client as modified with the client parameter DASDOVERRIDE), your backups can be written to an OVERFLOWDISKPATH which can also be specified in your profile definition. 

Backups to tape come from the pool defined in the POOL parameter of the profile definition. 

The UPSTREAM Storage Reservoir will automatically delete backups and release their associated tapes or disk storage based on values defined in the backup profile configuration.  This cleanup is performed whenever you do a backup for this profile or daily during system maintenance.  Note that the last full is always retained unless you specify DELETEEXPIREDLASTFULL.  The controlling parameter is RETENTIONTYPE.  If set to:

  • 0, UPSTREAM will maintain the number of backups defined in the RETAINCOUNT parameter. 
  • 1, UPSTREAM will maintain a backup for the number of days specified in the RETAINDAYS parameter. 
  • 2, UPSTREAM will maintain backups up to the number of tape sets defined in the RETAINCOUNT parameter.  For disk backups, if the number of tape sets are exceeded, the disk backups older than the oldest tape set are deleted.  If there are only disk backups, then the number of tape sets is never exceeded and they'll pile up infinitely.  Be careful using this option if you use disk backups.
  • 3, UPSTREAM will maintain RETAINCOUNT number of full backups.  When a full backup is deleted, the incrementals that occurred before it are also deleted.

To allow more efficient utilization of tapes UPSTREAM can place more than one backup on a tape.  If you specify NEWTAPEINCR N (which is the default), UPSTREAM will append incrementals after the first incremental onto the same tape set as the first incremental.  If you specify NEWTAPEFULL N (which is the default), UPSTREAM will append the full onto the same tape set as the incrementals.  The first incremental after a full always starts a new tape.

The scenario has a number of advantages.  It utilizes tapes more efficiently as multiple backups are stored on a single tape.  When the full is performed, if a file was backed up on an incremental and has not been changed at the time of the full, UPSTREAM will not recopy the file, but will note it on the tape and in the database, saving tape and improving performance.

Whenever a backup is expired the index files for the backup are deleted, if the backup is to disk then the backup file is deleted.  If the backup is to tape UPSTREAM will delete the index files for any expired backups.  However the tape will not be freed until all of the backups on the tape have been deleted.  You can recover any backups which are stored on a non-deleted tape using the Regen facility (see page 7-3).

If you wish to delete incrementals associated with older fulls, you can set the parameter EXPIREINCRFULLS.  This will count backwards from the current full and delete incrementals which precede the ‘n’ full.  This is particularly useful when backups are stored on disk.

Automatic garbage collection (which is when space is freed and backup tapes released) is performed whenever a backup requires a new tape or during system maintenance time, typically at 3:00 AM each day.

When planning for tape based backups, you must be sure to have sufficient free tapes available. 

If UPSTREAM inadvertently leaves a tape allocated but has no internal record for it, UPSTREAM will log at system maintenance time the tape number and recommend that you manually deallocate the tape.  We recommend that you examine the usserver.log file from time to time to see if any messages of this type have been logged.

For example, If you are backing up 20 machines all to tape, holding onto 5 weeks worth of backups, each machine runs on one tape and you are appending incrementals and fulls onto the same tapes, you will need a minimum of 100 tapes in the UPSTREAM pool.  However, to allow for growth, it is reasonable to add some additional tapes as well.

Thus you would specify in the GLOBAL.PRF or in separate backup profile definition files, RETENTIONTYPE 3 (number of full backups), RETAINCOUNT 5 (5 fulls). 

Disk based backups are never appended.  Each disk backup is a separate file placed in the UPSTREAM WORKPATH directory, in a subdirectory named for the backup profile, or in the DISKBACKUPPATH directory with the backup profile as the first component of the file name, in a file with the backup’s version date and the extension .backup.

When planning for disk based backups, you will need to allow sufficient disk space for all backups.

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